Learn the basics of secret key cryptography. This excerpt discusses data-scrambling techniques used in early cryptographic systems and elaborates on the concepts employed in modern cryptosystems. It also describes well-known contemporary algorithms and discusses the security services enabled through secret key cryptography.

This chapter is from the book

Introduction

Confidentiality is a data security property. Its primary goal is to confine
knowledge of information that the data represents within a particular set of
entities (such as human or a programmable electronic system) having the ability
to interpret the data. The process of achieving this confinement property,
otherwise known as secrecy, is by way of scrambling the plaintext form of data
into a reversible representation that perhaps has no syntax and certainly should
have no semantics.

Long before the advent of electronic systems, different methods of
data-scrambling transformations, known in contemporary terms as the science of
cryptography, were used. A cryptographic transformation of data is a
deterministic procedure by which data, in its plaintext form, is disguised to
result in a ciphertext representation that does not reveal the original data.
Similarly, the ciphertext can be reverse-transformed in a deterministic fashion
by a designated recipient so that the original data can be recovered.